aerial distribution and splitting

chris2k2

hi there, ive recently been on 2 courses.....city and guilds 2218 digital aerial installation and 2219 bskyb installation and health and safety.....ive yet to install any aerials or sat systems as im in the process of getting all the gear ready....

the aerial course was basicly direct from aerial to stb...which is the basics....

im just wandering about splitters and distribution as this will also be part of what i do......

from wat i gather the dvb-t signal strength should be around min 45dbuv - max 65dbuv at the stb or idtv.

ive got a rover st2 meter and most aerials ive measured so far are only outputting around 35-45 dbuv but getting a pass on signal quality..

this is where it starts to confuse me as if you start using f splitters to distribute the signal, surley this will lower the output quite a lot....and end up with poor signals.....

just wandering what you experienced installers are doing.? in my head , the proper way of doing things would be to use a mast head amp with the desired outputs and running the outputs to the rooms.?

this distribution lark is starting to get me all confused.......especialy with the min signal strength required being 45dbuv.....

any one help.?

cheers chris

satelliteman

The Rover ST2 / ST4 do seem to lock on rather lower recommended signal levels. Seen a lock on DVB-T multiplexes being as low as 36dBuV, as long as the MER and BER are reached it will load.

If planning or installing a distribution system, one needs to make sure that the minimum and maximum signal levels are reached at the outlet. For this you may need amplification or attenuation by using splitters.

Other things to consider when using amplifiers, ie. maximum output level and noise figures.

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CROSSBONES

or you could use a wider gain aerial to pull in a stronger signal

chris2k2

cheers for the replies.......would the following calculations be correct.?

say a customer wants an aerial with 4 aerial points around the house...

each aerial point requires 10 meters of cable.....

so im going to use a decent aerial, mast head amp 10db gain with 4 outputs....

say at the aerial we have a masurement of 45dbuv signal strength

after the mast head amp would we have 55dbuv on each output.? (as the gain is 10db)

then say 3db loss on each cable run, and 2 db say for connectors....

thats a 5db loss in total.

so........ 45dbuv + 10db(amp) - 5db (loss in cable/connectors) = 50dbuv at each outlet.?

is this correct or am i looking at this wrong.?

cheers chris....

ps ...dont want to look a numpty when i go out into the real world....lol

kenny1234

You're thinking along right lines

but

Of the 6 drt multiplexes more than likely all will have different power outputs.

I personally would use an aerial with more gain in your scenario, and try to get an average of 52 dbuv as an input level, as this is roughly mid way between min and max recommended dtt signal levels thus giving you lee-way should signal rise or fall due to atmospherics etc.

You could then either use a low gain 4 way amp or a 1 way amp into a 4 way splitter.

As a general rule with amps try to use lowest gain possible and create as much signal naturally with aerial.


I usually carry variable amps and power pass splitters on my van. This way I can control amp output levels and adjust to keep the system balanced.

In this months what satellite there is a good article re amplification

chris2k2

thank you, much appreciated......

Channel Hopper

Is this one of those fancy triangular aerials with remote power and integral 4 way splitter ?

If so, measure each output carefully, there are clones from the original Labgear version out there where the splitter isn't good, and the cable length can play havoc with the power supply voltage.




Whoa boy !

There is a very fine line between "hobby" and "mental illness"

nanochickin

From where you are the signal should be booming in off Sutton Coldfield.

I'm guessing you going to be getting at least 85-90dB on Analogue probably around 70dB on Digital.

You will get a way with just using a passive 4 way splitter with no need for a mast head amp.

Failing that you can use a 4 output Masthead amp. You can get the Vision 1420 4 Way amp from Eurosat in Walsall

Don't forget to buy the power supply too

We use Fracarro blu220 aerials for domestic properties and blu420 for IRS systems. We don't normally have that many problems

Don't worry you'll soon get the hang of it, Its when you get small distibution setups like the one below when it starts to become a bit of a headf**k

The piccie is just the head end, there was another 3 repeaters running from it, 128 points in total over 4 buildings. Not the neatest one i've ever done, but then again it was chucking it down with rain at the time and it was all shoved in a cab that really wasn't big enough for the job, hence the splitters being stacked on top of each other and the amp bolted to the side of the cab



Nano

Attached Thumbnails

 

satelliteman

Looks tidy enough there Nano

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chris2k2

thanks for the reply nano......thats one neat job in that photo.........

im just doing basics at the mo....aerial to 1 ,2 ,3 or 4 points at the moment......learning as i go......

i had one install with multiple trees in the way on a bungalow which needed to go to 2 rooms, readings were quite low on my meter so used a masthead 2 way amp which sorted that out.....then a neighbour came out saying i had a new aerial fitted 6 months ago, and now i cant get any channels..lol.....i said call the installer back then.....i know who installed it....he uses cheapo aerials 10 for about £45...

im using the triax digi 343 aerials at the moment which seem ok...ive had a few which are really strong , in the 70s for digi, so been putting attenuators on them......

as for splitting i did one as an experiment and learned a lot....i thought you would lose a lot more than 3-6dbuv on a 2 way splitter.....i take it 3 and 4 way will possibly be a little bit more....

we had a bad relationship with eurosat from our last encounters 5 years ago.....we now use grax...

i would really love to get into irs systems now ive been playing wiv the basics...

i am so busy at the moment with new installs and multiroom runs its unbelievable....

im gonna take my time on each and get them done properly to reduce call backs ...its taking me on average between 2-4 hours from arriving to leaving......thats a lot longer than i thought it would be.....

cheers chris

Channel Hopper

For two way at Group A frequencies, expect about 3dB, and up to 5dB at the higher end. Three way goes up to 5 and 8dB respectively, and four way can be anything between 7 and 11dB.

The type of splitter also can have a great effect on the overal drop per point, as can the method of connection. I usually stick to direct connection plastic surround boxes for London work, moving on to F plug metal units on other transmitters.

Eurosat started out on satellite kit, moving into aerial components when they realised the better profit margins. I buy off Alltrade myself as they have always delivered next day (usually at the end of the day, which is handy for me).

There is a very fine line between "hobby" and "mental illness"

satelliteman

Yes, for every doubling of splitter outputs, each leg will have a loss of approx -3dB + around 1dB device loss.

10 log N (Number of ports) + device loss of around 1dB works out to around the losses quoted above.

Losses also depend on the efficiency of the inductive transformer.

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chris2k2

thank you all thats a good bit of info......much appreciated.....